Utilization of multi-user, wireless communication systems to communicate telephonically has achieved wide popularity in recent years. Because a wireline connection is not required to effectuate telephonic communication, communication by way of a wireless communication system is possible at a location to which formation of wireline connection would be impractical or impossible.
Cellular communication systems having networks are exemplary of multi-user, wireless communication systems. Cellular communication networks, for instance, have been installed throughout significant portions of the world. Large numbers of subscribers to such cellular networks are able to communicate telephonically when positioned in areas encompassed by such cellular networks. Telephonic communication of both voice and data are permitted in such networks.
In a cellular communication system, fixed-site transceivers, referred to as base stations, are installed throughout a geographic region. Mobile transceivers, i.e., "cellular phones" or "subscriber units", positioned anywhere throughout the geographic area at which the base stations are installed, can communicate with at least one of the base stations. As a mobile transceiver travels through the geographic area, communication by the mobile unit is transferred, or "handed-off", to successive ones of the base stations. Continued communication by way of the mobile unit, without apparent interruption to the user is possible as the communication is handed-off between the successive ones of the base stations.
In some conventional, cellular systems, hand-offs are first initiated by a subscriber unit. The subscriber unit detects control signals generated upon selected control channels by the base stations. Comparisons are made at the subscriber unit between control signals received from various base stations. If communication between the subscriber unit and the cellular network by way of a first of the base stations is ongoing and the subscriber unit determines that communications can be better effectuated with the network by way of a another one of the base stations, the subscriber unit transmits a request that the ongoing communication be handed-off to the other base station.
Control circuitry, such as a mobile switching center, of the infrastructure of the cellular network typically controls the times in which a hand-off between two base stations is permitted. Responsive to the request transmitted by the subscriber unit, the control circuitry of the cellular network approves the hand-off, if such hand-off is possible.
If the hand-off request is approved, a channel at the other base station is allocated for communication with the subscriber unit, and instructions are sent to the subscriber unit instructing the subscriber unit to be re-tuned to the allocated channel. Communications by the subscriber unit thereafter continue with the cellular network by way of the succeeding base station. In such manner, ongoing communication is permitted without apparent interruption to the user of the subscriber unit.
Improvements in communication technologies have increased the convenience and affordability of usage of a cellular communication system. A concomitant increased number of users of the cellular communication systems increasingly utilize cellular communication systems to communicate therethrough. Other wireless communication systems have similarly exhibited increased usage. And usage of still other types of wireless communication systems is anticipated in the future.
Users, for instance, make use of cellular systems when positioned in motor vehicles. As many subscriber units are of sizes and weights permitting their carriage by a user, the subscriber units can be carried by a user and communication can be effectuated at any time. For instance, the user can communicate by way of the cellular system when positioned on a mass transit device.
When only a single user, or only a very small number of users, communicate pursuant to the cellular system while positioned on the mass transit vehicle, the additional loading to the cellular system is not significant. That is to say, when only a single or small number of users communicate by way of the cellular system when traveling together on the mass transit vehicle, only a single, or small number of, concurrent hand-off requests are made to the cellular network infrastructure as the mass transit vehicle upon which the user is situated travels through a geographic area.
However, when significant numbers of users positioned upon the mass transit vehicle utilize the cellular system, loading problems sometimes occur. Such loading problems can occur because the users situated on the mass transit vehicle are all positioned closely to one another to travel, together with travel of the mass transit vehicle, in the same direction, at the same speed, and at the same time.
Although each cellular phone is independently operable, all of the cellular phones receives the same, or similar, control signals from the base stations. And, even though each of the cellular phones is independently operable to determine when a hand-off request is made, because of the common positioning and movement of the cellular phones, each of the cellular phones substantially concurrently make hand-off requests to the cellular system network. Such concurrent requests can result in loading problems which might result in, e.g., inadvertent communication terminations.
Cellular communication systems have been constructed pursuant to various different cellular standards. The various different cellular standards are generally incompatible with one another. That is to say, a cellular phone operable pursuant to one cellular standard is typically unusable in a cellular communication system operable pursuant to a different one of the cellular standards. Some cellular phones, sometimes referred to as dual mode phones, have been constructed to permit their operation in two different cellular communication systems, such systems constructed pursuant two different cellular standards. However, the number of different cellular standards pursuant to which a cellular communication system might be constructed precludes, as a practical matter, the possibility that a portable, cellular phone might be constructed to permit its operation in every type of cellular communication system.
A cellular phone positioned upon a mass transit vehicle might be carried by the mass transit vehicle out of the geographic area encompassed by the cellular communication system in which it is operable and into a geographical area encompassed by a cellular communication system within which the cellular phone is incompatible. If communications are ongoing when the cellular phone passes beyond the coverage area of the cellular communication system in which the cellular phone is operable, communications are terminated. Communications are terminated even though communications would otherwise be possible if the cellular phone were operable pursuant to the cellular standard of the cellular communication system into whose coverage area the cellular phone travels. When a plurality of cellular phones are commonly carried upon a mass transit vehicle, numerous ongoing communications might be abruptly terminated as the mass transit vehicle carries the cellular phones out of the geographical area encompassed by one cellular communication system and into the geographical area encompassed by another cellular communication system.
A manner by which to reduce loading problems resulting when a plurality of users positioned to travel together at similar velocities during similar time periods would therefore be advantageous.
A manner by which to permit continued operation of a cellular phone as the cellular phone is carried out of a geographical area encompassed by one type of cellular communication system and into another type of cellular communication system would therefore also be advantageous.
It is in light of this background information related to multi-user communication systems, such as a cellular communication system, that the significant improvements of the present invention have evolved.